"AN IMPROVED HEAT AND CRUSH RESISTANT DATA RECORDER"

Abstract

The invention relates to an improved heat and crush-resistant data recorder, comprising: a metal chamber (2) having a first internal cavity (5); first means forming a thermal insulation (14) able to extend around the surface of the first internal cavity (5), and defining a second internal cavity (13); second means forming a thermal insulator / absorbent (20) able to occupy at least part of the second internal cavity (13); second means forming a thermal insulator / absorbent (20) able to occupy at least part of the second internal cavity (13), and to surround the data memory components (16), the second means forming a thermal insulator / absorbent having a solid to liquid phase transition at a high temperature; the second means forming a thermal insulator / absorbent (20) comprise a plurality of mats (20-1 to 20-7) of a predetermined thickness, arranged in stacks one against the other, at least one of the mats (20-4) being hollowed out to the form of the board (18) supporting the memory components (16) so that the said board (18) supporting the memory components (16), so that the said board (18) is housed in the said mat (20-4) thus hollowed out, the mat thus hollowed out being placed inside the stack.

Full Text

-1A-
The present invention concerns a data recorder resisting crushing and heat.
It finds an application in recorders installed in aeronautical, space, automotive, rail, and maritime vehicles and the like, which make it possible to acquire and record essential data relating to flight, journey or course, with a view to their possible recovery.
By reason of the fact that such recovery of data is sometimes made necessary in the case of an accident, this type of recorder must satisfy extremely stringent survival conditions, in particular as regards resistance to crushing and heat.
In a known manner, a data recorder comprises a metal chamber having a first internal cavity. A first thermal insulator generally extends around the surface of the first internal cavity and defines a second internal cavity. More frequently, a second thermal insulator/absorbent occupies the second internal cavity and surrounds the data memory components designed to be contained in the recorder.
The second thermal insulator/absorbent usually has a high solid to liquid phase transition temperature. For example, the second thermal insulator/absorbent is of the synthetic wax type, as in document EP-A-0 752 808.
Such recorders are complex in operation and have a high manufacturing cost. In addition, the synthetic wax is generally lacking in stability and conductivity at the temperatures indicated in standards on the ability to survive heat, where constraints are increasingly exacting. For example, in the document EP-A-0 752 808, the solid to liquid phase transition takes place between 105°C and

2
130°C. The wax moreover represents a considerable mass which produces additional constraints.
Moreover, in the liquid state, the wax increases in volume and exerts pressures which cannot be withstood by the soldered joints of electronic circuits, which makes necessary a device for the controlled escape of wax from the box.
Moreover, in document EP-A-0 752 808, thermal protection makes use of magnesium sulfate in an accompanying cavity, trapping water which is vaporized. Two fuses with a melting point of 104°C are provided for the removal of water vapour.
In document EP-A-0 550 345, thermal protection is obtained with the aid of a reservoir of material disposed between the inner box and an envelope. The reservoir of material is a solid possessing mechanical strength containing water which can be liberated under the action of heat.
The vaporization of water produces here problems of removal of liquid and/or pressure equilibrium which are difficult to resolve and make the application of thermal protection complex.
The Applicant has addressed the problem of overcoming these disadvantages. The present invention precisely provides a solution to this problem.
It concerns a data recorder resistant to crushing and heat in case of accident, of the type comprising :
- a metal chamber having a first internal cavity;
- first means forming a thermal insulation able to extend
around the surface of the first internal cavity, and
defining a second internal cavity;

3
- second means forming a thermal insulator/absorbent able to occupy the second internal cavity, and to surround the data memory components, the second means forming a thermal insulator/absorbent having a solid to liquid phase transition at a high temperature.
According to a general definition of the invention, the second means forming a thermal insulator/absorbent consist of a material containing ceramic fibres and an inorganic endothermic material, the solid to liquid phase transition taking place without liberation of a liquid product.
According to the invention, the thermal protection has the advantage of using a solid to liquid phase transition without liberation of a liquid product. Vaporization of water is thus not used in the thermal protection according to the invention, which eliminates any problem of the evacuation of liquid and/or pressure equilibrium.
Similarly, according to the invention, there is no need for a sealed chamber or protection against the products used, since the materials used according to the invention are not aggressive. The result is a high degree of simplicity in application with easy installation of memory boards, which accordingly reduces the costs.
Such a material, according to the invention, has the advantage of retaining its thermal insulation and absorption properties over a range of temperature extending from a few °C up to a high temperature of the order of 220°C. Moreover, such a material maintains its thermal insulation and absorption properties over a period of several hundreds of hours when it is subjected to a high temperature, for example of the order of 95°C.
In practice, the thermal insulating, absorbing material is marketed by the 3M company under the reference 3M INTERAM
E-5A.

4
Surprisingly, the Applicant has observed that such a material normally used for the passive protection against fire on electric cables or on steel structures may also serve as a protection for memory components of a data recorder.
Moreover, the Applicant has studied and verified that the thermal properties of this material as regards thermal insulation and absorption are perfectly retained up to a high temperature of the order of 220°C, which is appreciably greater than the limiting temperature for the normal functioning of the memory components which are generally used in this type of data recorder.
According to a first embodiment of the invention, the means forming an insulator/absorbent comprise a plurality of mats of a predetermined thickness, arranged in a stack one against the other, at least one of the mats being hollowed out to the form of the boards supporting the memory components, so that the said board is housed in the said mat thus hollowed out and placed inside the stack.
For example, the hollowed out mat is placed between at least two mats.
Advantageously, the stack of mats is enveloped in an envelope of plastic material, the free ends of the envelope being able to project from the chamber after insertion of the stack so as to constitute tabs facilitating the extraction/insertion of the stack of mats in the chamber, the envelope moreover ensuring compression when the mats are inserted in the chamber and residual compression after insertion.
Preferably, the chamber includes an appendage secured to the said chamber and comprising means forming a support able to support an acoustic or similar beacon.

5
In practice, the memory components are of the static type, for example EEPROM.
Preferably, the first means forming a thermal insulator consist of a fibrous material and fine particles, marketed under the reference MIN-K by the THERMAL CERAMICS COMPANY or under the reference MICROTHERM.
Preferably, the chamber is made of steel.
Other features and advantages of the invention will become apparent in the light of the following detailed description and drawings in which :
- figure 1 is a perspective view of the chamber and of the
first thermal insulator according to the invention;
- figure 2 is an exploded view of the different components
constituting a recorder according to the invention; and
- figure 3 represents curves illustrating the heat flow
absorbed by the second insulator/absorbent of the invention
as a function of temperature.
The accompanying drawings include, for various purposes, information of a certain character. They may consequently not only serve for the better understanding of the following detailed description, but also contribute to the definition of the invention where appropriate.
With reference to figures 1 and 2, the recorder of the present invention comprises a metal box 2, which is relatively small in size, and relatively light in weight. Preferably, the box 2 has dimensions compatible with a box of the 1/2-ATR type so as to be mounted on a support commonly used in aeronautics.

6
It should be noted that the recorder may be used, not only
in an aeronautical environment, but also for maritime, rail, automotive, space or similar vehicles.
The metal box 2 defines a first internal cavity 5.
For example, the metal box 2 is constructed in steel or another material which has a relatively low density, a relatively high thermal conductivity and a relatively high resistance to crushing and to penetration.
The metal box 2 is designed to be closed by a lid 6, equally made of a metallic material and preferably steel.
The free edge of the open box 2 has flat lips 4 on which fixing holes 10 are provided. The lid 6 is designed to be assembled to the lips 4 by means of screws 8 capable of being inserted into the fixing holes 10 of the flat lips. Other conventional means of attachment can be applied.
In practice, the internal cavity 5 defined by the box 2 has a parallelepiped shape with rounded angles.
Advantageously, the box 2 has an appendage 12 secured to the box 2. This appendage is intended to support a maritime acoustic beacon (not shown). For example, the support 12 comprises 4 circular jaws designed to receive a
cylindrical beacon.
A thermal cladding 14 is housed inside the cavity 5. A thermal cladding of this type constitutes a first thermal barrier.
The thermal cladding 14, having a thickness of the order of 2 to 3 cm, forms a cavity 13 extending inwards.
The thermal cladding 14 preferably has a unitary structure, formed of a moulded solid material. A thermal cladding of

7
this type constitutes a good thermal insulator, i.e. it has a low thermal conductivity and a relatively low density.
In practice, the thermal cladding 14 is a combination of a
fibrous material and very fine particles.
For example, the cladding 14 is the product marketed under the reference MIN-K of the type 1303 by the THERMAL CERAMICS company, or MICROTHERM.
The memory components 16 are for example connected to a printed circuit board 18 of the double sided type.
In practice, the memory components 16 are of the static type, for example EEPROM. The printed circuit board 18 includes a connector {not shown) enabling a bundle of wires 11 to be connected to an external electronic system (not shown) via a slot 9 provided in the lid 6.
Advantageously, the components 16 of the printed circuit boards 18 are protected against water with the aid of a suitable varnish.
According to the invention, in order to make it possible to obtain a high degree of thermal protection, the printed circuit board 18 is additionally housed in a stack of mats, shown individually in 20-1 to 20-7, and of which 20-4 is hollowed out in the form of the board 18.
In order to simplify matters, only one printed circuit board is housed in the chamber. Quite obviously, according to the applications, for example in maritime use, the recorder may contain several boards which will then be protected according to the invention, as is the board 18.
For example, the mats 20 are in general parallelepiped in shape. The dimensions of the mats are substantially greater than those of the printed circuit board 18.

8
According to the invention, the mats 20 consist of a material of the thermal insulator/absorbent type containing ceramic fibres and an inorganic endothermic material.
In practice, this material is marketed by the 3M company under the reference 3M INTERAM E-5A, with an alternative E-5A-3 (7.6 mm) or E-5A-4 (10.2 mm) according to the
thickness of the mats.
Surprisingly, the Applicant has observed that such a material normally used for passive protection against fire on electrical cable or on steel structures may also serve to protect memory components in a data recorder.
In addition, the Applicant has studied and observed that the thermal properties of this material as regards thermal insulation and absorption, are perfectly retained up to a high temperature of the order of 220°C corresponding to a temperature which is appreciably greater than the limiting temperature for the normal functioning of the memory components which are generally used in this type of data recorder.
With reference to figure 3, four curves Cl to C4 have been shown illustrating the heat flow absorbed by a mat of the E-5A-3 type as a function of temperature.
The curve Cl illustrates the heat flow absorbed by a mat E-5A-3 as a function of temperature, without special previous treatment.
The curve C2 illustrates the heat flow absorbed by a mat E-5A-3 as a function temperature, after having been subjected for 24 hours to a temperature of 95°C.
The curve C3 illustrates graphically the heat flow absorbed by a mat E-5A-3 as a function of the temperature, after

9
having been subjected for 240 hours to a temperature of 95°C.
The curve C4 illustrates graphically the heat flow absorbed by a mat E-5A-3 as a function of temperature, after having been subjected for 600 hours to a temperature of 95°C-
Each curve is characterized by a first region of temperature PCI, extending from a few degrees °C to 220°C, in which the heat flow absorbed by the material 20 is relatively constant. This constant shows that the material is inert in this range PC1.
On each curve, a first peak TM1 can be observed around 220 to 240°C, with a large increase in absorbed thermal energy.
Each curve is additionally characterized by a second region of temperature PC2, extending from 250°C to 300°C, in which the heat flow absorbed by the material 20 is relatively constant.
A second peak TM2 can also be observed around 330°C, with a large increase of absorbed thermal energy.
Finally, a third region PC3 can be observed extending from 350°C and above, in which the energy absorbed is relatively constant.
Reference will once again be made to figures 1 and 2.
The mats 20 are arranged in a stack, one against the others in parallel with the large lateral faces of the box 2. The mat 22-4 is hollowed out into the form of the board 18 supporting the memory components, so that the said board 18 is housed in the said mattress hollowed out in this way.

10
Advantageously, the mat 20-4 hollowed out in this way is placed inside the stack. For example, with reference to figure 2, the mat 20-4 is placed between the three mats 20-1 to 20-3, and the three mats 20-5 to 20-7.
Very advantageously, the stack of mats is enveloped in an envelope of plastic material 30, for example made of polycarbonate. The free edges 32 of the envelope are able to project from the chamber after insertion of the stack in the chamber so as to constitute tabs facilitating the extraction/insertion of the stack of mats.
Moreover, this envelope made of plastic material ensures compression when the mats are inserted in the chamber, as well as a residual compression after insertion.
Finally, a lid of insulating material 32 covers the stack of mats thus inserted in the chamber before application of the lid 6 on the lips 4 of the metal box 2.
The lid made of insulated material 32 is constructed with the same material as the thermal cladding 14. The lid covers the open face of the box containing the stack of mats, so as to cover the box completely and in this way to close the box with the aid of the lid 6.
By virtue of the invention, the recorder complies with the requirements indicated in the document TSO C-124a (Technical Standard Order) issued by the American Administration (FAA) and which concern survivability tests of recorders in case of accident.
The total thickness of the assembly formed by the thermal cladding 14 and the mats 20 as well as the volume occupied by the said mats determines the degree of thermal protection conferred.

11
In commerce, the mats E-5A are normally sold with a sheet of aluminium on one of the faces. The Applicant has observed that it is preferable to remove this sheet of aluminium.

12 We Claim
1. An improved heat and crush-resistant data recorder, comprising:
- a metal chamber (2) having a first internal cavity (5);
- first means forming a thermal insulation (14) able to extend around
the surface of the first internal cavity (5), and defining a second
internal cavity (13);
- second means forming a thermal insulator / absorbent (20) able to
occupy at least part of the second internal cavity (13);
- second means forming a thermal insulator / absorbent (20) able to
occupy at least part of the second internal cavity (13), and to
surround the data memory components (16), the second means
forming a thermal insulator / absorbent having a solid to liquid
phase transition at a high temperature;
- characterized in that the second means forming a thermal insulator
/ absorbent (20) comprise a plurality of mats (20-1 to 20-7) of a
predetermined thickness, arranged in stacks one against the other,
at least one of the mats (20-4) being hollowed out to the form of
the board (18) supporting the memory components (16) so that
the said board (18) supporting the memory components (16), so
that the said board (18) is housed in the said mat (20-4) thus
hollowed out, the mat thus hollowed out being placed inside the
stack.
2. The data recorder as claimed in claim 1, wherein the second means
forming a thermal insulator / absorbent (20) consist of a material
containing ceramic fibres and an inorganic endothermic material, the solid
to liquid phase transition taking place without liberation of a liquid
product.

13
3. The data recorder as claimed in claim 2, wherein the second means
forming a thermal insulator / absorbent (20) retain their absorbent
property over a range of temperature extending from a few degrees
Celsius up to a high temperature of the order of 220° C.
4. The data recorder as claimed in claim 3, wherein the second means
forming a thermal insulator / absorbent (20) retain their absorbent
property when they are subjected to a high temperature for a period of
several hundred hours.
5. The data recorder as claimed in claim 1, wherein the hollowed mat is
placed between 3 mats on either side.
6. The data recorder as claimed in one of the preceding claims, wherein the
stack of mats is enveloped in an envelope (30) of plastic material, the free
ends (32) of the envelope (30) being able to project from the chamber
after insertion of the stack in the chamber so as to constitute tabs
facilitating the extraction / insertion of the stack of mats in the chamber,
the envelope additionally ensuring compression when the mats are
inserted in the chamber as well as residual compression after insertion.
7. The data recorder as claimed in one of the preceding claims, wherein the
chamber (2) comprises an appendage secured to the said chamber and
having means forming a support (12) able to support an acoustic or
similar beacon.
8. The data recorder as claimed in one of the preceding claims, wherein the
memory components (16) are of the static type.

14
9. The data recorder as claimed in one of the preceding claims, wherein the first means forming thermal insulation (14) consist of a material of the passive insulating type, of the MIN-K or MICROTHERM type.
10.The data recorder as claimed in one of the preceding claims, wherein the chamber (2) is made of steel.
11.The data recorder as claimed in one of the preceding claims, wherein the mats are not covered with an aluminium sheet.
12.A vehicle for one of aeronautical, maritime, rail, space and motor incorporating the recorder as claimed in any of the preceding claims.
The invention relates to an improved heat and crush-resistant data recorder, comprising: a metal chamber (2) having a first internal cavity (5); first means forming a thermal insulation (14) able to extend around the surface of the first internal cavity (5), and defining a second internal cavity (13); second means forming a thermal insulator / absorbent (20) able to occupy at least part of the second internal cavity (13); second means forming a thermal insulator / absorbent (20) able to occupy at least part of the second internal cavity (13), and to surround the data memory components (16), the second means forming a thermal insulator / absorbent having a solid to liquid phase transition at a high temperature; the second means forming a thermal insulator / absorbent (20) comprise a plurality of mats (20-1 to 20-7) of a predetermined thickness, arranged in stacks one against the other, at least one of the mats (20-4) being hollowed out to the form of the board (18) supporting the memory components (16) so that the said board (18) supporting the memory components (16), so that the said board (18) is housed in the said mat (20-4) thus hollowed out, the mat thus hollowed out being placed inside the stack.